Dynasonics MFX Series Insertion MagProbe Flow Meter - Manual (Page 21)

Rev. 01/11 -1.19- MFX
The Rate Pulse Output Module is utilized to transmit information to
external counters and PID systems via a frequency output that is
proportional to system flow rate. The frequency output range of the
Rate Pulse Module is 0–2,500 Hz. This module has two types of
outputs: one simulates the output of the coil of a turbine flow meter,
and the other is an open-collector type that does not source voltage
at its output. Both outputs may be connected simultaneously.
The turbine meter output creates a 500 mV peak-to-peak saw-tooth
waveform that is not referenced to ground. This output can be run to
electronic monitors that are compatible with variable reluctance
outputs from coils, such as those found in turbine and paddle-wheel
flow meters. The input impedance of the receiving device should not
be smaller than 2,000 Ohms.
The standard pulse output does not output a voltage, but acts as an
“open-collector” output requiring an external power source and pull-
up resistor. See Figure 1.13. The MOSFET in the Rate Pulse
Module can support loads of 100 V @ 1A. Resistor selection is
based on the input impedance of the receiving device. Select a
resistor that is a maximum of 10% of the input impedance of the
receiving device, but do not exceed 10k Ohms.
PART 1 - ISO-MOD
Rate Pulse
Figure 1.13
Rate Pulse Module